In various inspection and object locating applications it is important to be able to determine the surface contours of an object in three dimensions, or the location of key features on the surface of an object in three dimensions, or the gross location of an object in three dimensions.
Existing range sensing methods include:
(1) Structured light methods--projecting a fixed pattern onto an object and looking for perturbations in this pattern, from which range information can be inferred.
(2) Triangulation--transmitting light rays from a transmitter onto the object under study and detecting reflections of the rays onto a receiver such as a line scan CCD array located some known distance away from the transmitter. The location of the reflected ray on the array is a measure of the distance between the transmitter and the point on the object from which the ray is reflected.
(3) Laser radar and time of flight--reflecting a collimated, pulsed beam of light off of a point on an object, measuring the flight time of the pulse to and from the transmitter, and determining the distance between the transmitter and the point directly from the flight time.
(4) Stereo--simultaneously viewing the object of interest by means of two or more imaging devices located some known distance apart and using the disparity in image location, from imager to imager, of a given feature on the object in order to determine the distance from the imagers to the feature.
(5) Autofocusing techniques--maximizing the sharpness of edges in an image by adjusting the focal length of the imager and using the focusing adjustment to gauge the distance between the imager and object being viewed.
It is an object of the instant invention to provide a method and apparatus for determining the distance to an object by measuring the separation of dual images of the object.
It is another object of the invention to provide a method and apparatus for determining a third dimension of a surface profile by measuring the separation between dual two dimensional images of various points on the surface.
Still further, it is an object of the invention to provide simplified method and apparatus for determining the coplanarity of points on a plurality of projections of an object.
These and other objects of the invention will become more apparent from the following specification, claims, and drawings.